The invention relates to a multi-purpose power actuated valve for supplying secondary air to an exhaust system of an internal combustion engine.
As a rule, for the treatment of exhaust gases from an internal combustion engine, secondary air is supplied to the exhaust gas, with the result that the pollutants in the exhaust gas are reduced because of further exothermal reactions in the exhaust system. Furthermore, a catalytic converter, which may be present in the exhaust system, is heated up. For this purpose, a secondary-air pump is used, which is connected with its discharge side to the exhaust gas duct via a secondary-air switching valve. The secondary-air switching valve is combined with a non-return valve so as to prevent exhaust gas from entering the secondary-air duct in operating phases in which the pressure of the secondary-air pump is lower than the exhaust gas pressure or when the secondary-air pump is not in operation.
The components of the secondary-air supply system have to be protected against the hot exhaust gases, since they would be damaged, and, under certain conditions, an engine fire could occur due to a flame flashback. In order to protect the secondary-air switching valve itself against damage from the hot exhaust gases and ensure its operating reliability, it is known from DE 197 31 622 A1 to provide for the secondary-air switching valve, which, as a rule, is vacuum- or pressure-controlled, an additional non-return valve, which is arranged between the secondary-air switching valve and the exhaust system.
Furthermore, DE 42 04 415 A1 discloses a multi-purpose valve, in particular for secondary-air pumps in internal combustion engines with a regulated three-way catalytic converter. Said valve has a valve housing which is provided with a valve inlet and a valve outlet and in which a pneumatically actuated cutoff valve and a non-return valve located downstream of the latter in the direction of flow are integrated. This type of multi-purpose valve is designated below as a “pneumatic multi-purpose valve”. At the present time, novel multi-purpose valves are being developed, which consist of an electrically actuated cutoff valve and, like-wise, of a non-return valve located downstream of the latter in the direction of flow. This type of multi-purpose valve is designated below as “electrical multi-purpose valve”.
The housing of the pneumatic or electrical multi-purpose valve is subdivided, in the region of a non-return valve plate, into a housing upper part and a housing lower part, the non-return valve plate being held between the two housing parts. The outlet of the multi-purpose valve is arranged axially parallel, or at an angle, to the passage orifices in the non-return valve plate and a duct part widens in a funnel-like manner toward the passage openings.
In newer internal combustion engines with exhaust gas turbochargers, the exhaust gas temperature and exhaust gas pressure may be so high that, under certain circumstances, the prescribed specifications can no longer be maintained by the known secondary-air switching valves or multi-purpose valves.
It is the object the invention to improve the useful life of a multi-purpose valve while it can accommodate higher exhaust gas pressures and/or exhaust gas temperatures and, in the case of the electrical multi-purpose valve, to improve the electrical design, or, in general, to make it possible to permit their use in certain sensitive locations.